Dislocations at / interfaces, where the  grains were related by a 120 rotation about <111>, were studied by means of high-resolution electron microscopy. Arrays of super-partial dislocations were observed at interfaces which were dissociated into 2 Shockley partial dislocations, separated by a region of intrinsic stacking fault. Interfacial dislocations were expected to be required at these interfaces in order to accommodate interfacial misfit, because c/a was not equal to unity for the  matrix. Further dislocations could cross-slip from the bulk, and into the interface, due to the difficulty of dislocation propagation across 120 interfaces. Screw ½<¯1¯12>1  ½<¯12¯1>2 and ½<¯110>1  ½<10¯1>2 dislocations had previously been observed at 120 interfaces by means of weak-beam transmission electron microscopy. The present high-resolution electron microscopic study indicated that screw ½<10¯1>1  ½<0¯11>2 super-partials also existed at such boundaries. The latter super-partials, and others, could not cross-slip out of 120 interfaces because they would trail antiphase boundaries and never be observed as isolated dislocations in the bulk. The present super-partials therefore had to originate either as original misfit dislocations from the original    transition, or as the result of dislocation interactions at the interface.

B.J.Inkson, C.J.Humphreys: Philosophical Magazine A, 1996, 73[5], 1333-45